Apparatus for the wet extrusion of solutions of polymers of vinyl chloride exhibiting a high degree of syndiotacticity



June 25, 1968 F. DENTI ETAL 3,389,428

APPARATUS FOR THE WET EXTRUSION OF SOLUTIONS OF POLYMERS OF VINYL CHLORIDE EXHIBITING A HIGH DEGREE OF SYNDIOTACTICITY Filed Sept. 24, 1963 2 Sheets-Sheet l \-N 1 k I T 254M M424 ATTORNEY June 25, 1968 DENT| ET AL 3,389,428

APPARATUS FOR THE WET FIXTRUSION OF SOLUTIONS OF POLYMERS OF VINYL CHLORIDE EXHIBITING A HIGH DEGREE OF SYNDIOTACTICITY Filed Sept. 24, 1965 2 Sheets-Sheet 2 Q: :9 N fwm' AIM ATTO R N EY United States Patent Italy Filed Sept. 24, 1963, Ser. No. 310,992 Claims priority, application Italy, Sept. 27, 1962, 1 8/ 2 1 Claim. (Cl. 18-8) The present invention relates to apparatus for the wet spinning of polymer solutions, and in particular apparatus which does not require the spinning device to be dipped into the coagulum bath. More particularly, the invention relates to an apparatus for wet spinning vinyl polymer solutions which may be successfully used where it is necessary, for example, to maintain the spinning device separate from the coagulum bath, to maintain the temperature of the solution higher than that of the coagulum bath, or to prevent the material forming the spinneret holder being attached by the coagulum bath.

One of the principal applications of this invention is the wet spinning of solutions of vinyl chloride polymers exhibiting a high degree of syndiotacticity, in which cases it is necessary to maintain the spinning solution at high temperature, at least over 80 C. e.g., in the range of about 90 to 150 C. while maintaining the temperature of the coagulum bath considerably lower, e.g., in the range of about 30 to 80 C. and usually less than 60 C.

The phrase polymers of vinyl chloride exhibiting a high degree of syndiotactieity, as used in the present description, should be understood to embrace homopolymers of vinyl chloride having a syndiotacticity degree greater than 2 (the degree of syndiotacticity determined by the absorption bands ratio LR. D635 and D692 cmr see Burleigh ].A.C.S., 82 page 7494960), as well as its copolymers and their mixtures comprising at least 85% vinyl chloride by weight.

In general, the equipment usually employed in wet spinning of polymer solutions consists of a spinning device mounted to suitable spinner holders, the entire combination being adaptable for complete immersion into the coagulum bath.

In the known methods, the dope is fed to each spinning device by means of a spin-metering pump connected to the main duet through which the dope flows from the storage tanks. It is readily observable that this type of spinning device is quite unsuitable where the spinning device should be maintained separate from the coagulum bath. Moreover, spinning devices of this type are unsuitable for Wet spinning of vinyl chloride polymers having a high degree of syndiotacticity, which require a coagulum bath maintained at a temperature definitely lower than that of the dope; as matter of fact it is known that soluions of vinyl chloride polymers exhibiting a high degree of syndiotacticity have the tendency to gel at fairly high temperatures, therefore during the passage in a coagulum bath maintained at low temperature as above said, the solutions gel immediately.

The gel temperature is strictly related to the stereo regularity of the product, hence to the polymerization temperature and quantity of polymer present in the solution. By way of example, a solution having 18% polymer and a syndiotacticity degree of about 2.2, and an intrinsic viscosity of 1.3, abruptly gels at about 90-95 C., while a solution at 20% of the same polymer gels at 105-110 C.

On the other hand, coaguluant mixtures, which prove more effective in the spinning of vinyl chloride polymers having a high degree of syndiotacticity, comprise rather volatile compounds, which must be maintained at temperatures in the range of about 3080 C. in order to avoid excessive evaporation of the same with a consequent increased cost of the finished product, which would render the process commercially uneconomic. Furthermore it has been experimentally proved, in cases in which non volatile compounds have been employed as coagulant mixtures, that the coagulum is better and brighter and more compact fibers are obtained, if the coagulation is carried out at temperatures lower than 50-60 C.

It follows, therefore, that the standard spinning devices in which the spinneret is completely dipped into the coagulum bath is not suitable because, if it is operated at high enough temperature to avoid gelling of the polymer solution, because of evaporation, a heavy loss of the compounds constituting the coagulum bath occurs, and if it is operated at low temperatures, gelling of the dope occurs due to the inevitable cooling which occurs prior to the extrusion from the feeding pipe to the spinning device, thereby making it impossible to spin the material.

According to the present invention, the foregoing disadvantages and many other disadvantages common to known apparatuses and processes have been eliminated. In accordance with the invention, an apparatus and method is provided for spinning of polymer solution in which the surface contact between the spinning device, hence dope to be spun, and the coagulum bath is extremely limited, that is, limited strictly to the external surface of the spinneret.

Further, the spinning apparatus of this invention allows the spinning of polymer solutions requiring the maintainance of high temperatures until the moment of extrusion, and a coagulum bath at considerably lower temperatures.

Another advantage derived from apparatus of this invention lies in the improved filterability of the solution because the solution is more fluid, being the temperature maintained high, which in turn makes it possible to use very thin filters, avoiding thereby, clogging of the spinneret holes, and improving the evenness and final characteristics of the obtained fibres.

Other objects and advantages will become apparent in the following discussion. For a better understanding of the invention, reference is now made to the drawings, wherein:

FIGURE 1 is a diagrammatic perspective view showing a wet spinning apparatus according to this invention.

FIGURE 2 is a sectional view of a spinning head suitable for use in this invention.

With reference to the drawings wherein like parts have the same numerals and with particular reference to FIG- URE 1, the spinning solution coming from tank by means of general duct 1, passes into the metering pump 2, and after filtering into the filter 3, it goes to the spinning de vice 4, which is screwed, flanged or coupled by means of a system which assures a perfect sealing to the spinneret holder 5 directly coupled to tank 6, which contains the coagulum bath. In such a manner, the contact between the spinning solution and the coagulum bath is limited .to the external surface of the spinneret.

A heating jacket 7, in which hot oil is being circulated (entering at 8 and coming out at 9), and in which is included metering pump 2, filter 3 and spinning device 4, allows the solution to be maintained at the desired temperature.

Tank 6 is provided at the lower part with a discharge valve 12, which allows the discharge of the coagulum bath every time it calls for a cleaning or a checking of the spinning device.

The yarns 10, coming from the spinning device, are coagulated in a suitable bath deviated from roller 11 and are subjected to appropriate treatment.

An example of a practical embodiment of parts 3, 4 and 5 of the preceding figure is shown in FIGURE 1, which shows a sectional view of the spinning head, object of this invention. With reference to said figure, the dope coming from tube 13 is filtered under heat in a plug filter 14 and is then filtered in a disk-filter 15, which is supported by plate 116, finally being extruded through spinneret 17. The whole block is kept heated by sleeve 18, wherein vapor or hot oil is circulating entering at 18' and coming out at 18".

Sleeve 18 is fixed to wall 19 of the coagulation tank by means of bolts 20 and 26', while tightness of the coagulation tank is ensured by a toroidal gasket 21.

This gasket 21 is pressed against wall 19 by a cylindrical body 19, which is pushed by a threaded rod 22 which in its turn is engaged on the tilting bracket 23 mounted in a turning way on pivot 23.

it was experimentally proved that spinning with a normalty used spinning device solution of polyvinyl chloride at high syndiotacticity degree in an organic solvent such as: cyclo-hexanone, dimethylformamide, dimethylacetamide, nitrobenzene and the like, and using as a coagu lum bath a mixture of solvent and one or more precipitants such as: Alcohols, ketones, acids, amides or the like, after 10 minutes the spinning must be interrupted because of the clogging of the spinneret holes. Such clogging is due to gelling of the dope before its being extruded.

On the other hand, by employing a coagulum bath conto have the compounds of the bath itself evaporated, a continuous operation and an evenness in the spinning can be ensured.

We claim:

1. Apparatus for forming fibres, filaments and yarns by wet-spinning of solutions of polymers of vinyl chloride having a degree of syndiotacticity greater than 2, wherein the polymer solution must be maintained at a temperature higher than that of the coagulum bath, comprising a tank for holding the coagulum bath provided with an opening in its side wall; a sleeve fixed to said tank side Wall and having an end in registry with the opening in said side wall; a metering pump for the spinning solution, a filter and a spinneret connected in sequence and enclosed by said sleeve with the spinneret directed to deliver the spinning solution through said opening in the tank side wall; means securing the spinncret in the end of said sleeve and in relation to the opening in the tank side Wall so that the surface contact between the spinneret and coagulum bath is limited only to the external frontal surface of the spin neret; and means for circulating a heat transfer fluid through said sleeve in heat transfer relationship with said metering pump, filter and spinneret.

References Cited UNITED STATES PATENTS Re. 20,080 8/1936 Robertson 264203 2,367,493 1/1945 Fordyce et al. 264-203 2,984,593 5/1961 Isaken et al 260-304- X 3,011,859 12/1961 Knudsen 264203 3,044,115 7/1962 Craver et a1. 264-183 3,206,529 9/1965 Heijnis 264--178 3,222,317 12/1965 Kauder 260-304 FOREIGN PATENTS 3,721,113 5/1962 Japan.

ALEXANDER H. BRODMERKEL, Primary Examiner.

40 J. H. WOO, Assistant Examiner. 

1. APPARATUS FOR FORMING FIBRES, FILAMENTS AND YARNS BY WET-SPINNING OF SOLUTIONS OF POLYMERS OF VINYL CHLORIDE HAVING A DEGREE OF SYNDIOTACTICITY GREATER THAN 2, WHEREIN THE POLYMER SOLUTION MUST BE MAINTAINED AT A TEMPERATURE HIGHER THAN THAT OF THE COAGULUM BATH, COMPRISING A TANK FOR HOLDING THE COAGULUM BATH PROVIDED WITH AN OPENING IN ITS SIDE WALL; A SLEEVE FIXED TO SAID TANK SIDE WALL AND HAVING AN END IN REGISTRY WITH THE OPENING IN SAID SIDE WALL; A METERING PUMP FOR THE SPINNING SOLUTION, A FILTER AND A SPINNERET CONNECTED IN SEQUENCE AND ENCLOSED BY SAID SLEEVE WITH THE SPINNERET DIRECTED TO DELIVER THE SPINNING SOLUTION THROUGH SAID OPENING IN THE TANK SIDE WALL; MEANS SECURING THE SPINNERET IN THE END OF SAID SLEEVE AND IN RELATION TO THE OPENING IN THE TANK SIDE WALL SO THAT THE SURFACE CONTACT BETWEEN THE SPINNERS AND COAGULUM BATH IS LIMITED ONLY TO THE EXTERNAL FRONTAL SURFACE OF THE SPINNERET; AND MEANS FOR CIRCULATING A HEAT TRANSFER FLUID THROUGH SAID SLEEVE IN HEAT TRANSFER RELATIONSHIP WITH SAID METERING PUMP, FILTER AND SPINNERET. 